This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Aspergillus fumigatus is a saprophytic filamentous fungus that is the most frequent causative agent of invasive opportunistic mould infections in immunocompromised patients. We currently do not understand the mechanisms used by A. fumigatus to survive and cause disease in immunocompromised hosts. During mammalian pathogenesis, all pathogenic microbes are exposed to rapidly changing oxygen levels. Oxygen is the critical electron acceptor in aerobic respiration and organisms must possess alternative mechanisms to deal with low oxygen (hypoxic) conditions found at sites of infection in vivo. Our hypothesis is that A. fumigatus utilizes an alcohol fermentation pathway to survive inflammatory responses found in vivo in pulmonary invasive aspergillosis. This hypothesis is founded on preliminary data from metabolomics studies of A. fumigatus infected murine broncheoalveolar lavages showing the production of ethanol in vivo during fungal infections. We are exploring whether this alcohol fermentation pathway is important for A. fumigatus to cause disease by creating genetic mutants of A. fumigatus deficient in their ability to respond to low oxygen conditions via the use of an alcohol fermentation pathway. We currently have identified the genes and generated mutants deficient in these genes that are involved in alcohol fermentation in A. fumigatus. In the past year, we have examined the ability of these alcohol deficient strains for fungal virulence and found that loss of alcohol fermentation does not affect the virulence capability of A. fumigatus. Additional mechanisms of electron transport under hypoxic conditions are the likely explanation for this result and are currently being explored. The results of this proposal have potential clinical significance via direct manipulation of oxygen levels at sites of fungal infection and also the potential to generate increased efficacy of current antifungal drugs.